Easy, assuming each game copy has a unique key. Then you can do it in software quite easily. "Opps, sorry, Update 6.2.1.7 has detected that this game was registered to more than one console and is no longer playable."

Sure, someone might hack it, but for the vast majority of consumers that would make being able to play a used game a thing of the past.

Actually, according to this article in Wired [wired.com] the PS4 will be able to do it both ways. Publishers have the option of "registering" their games. Guess which they'll do? This is just a marketing ploy for Sony to be able to say "We aren't disabling used games, the publishers are!

I did use the other os feature. I'm a software developer it was very useful as a development testing platform. I also had it setup at one put to be a 3D rendering node for some of my hobby 3D modelling. until my cousin and wife put in a bluRay we rented. I was upstairs making snacks when they ran the update. I was pretty pissed. My wife at least should have known better. No use crying over spilt milk, I haven't even turned the console on since we watched that movie. I only own one other bluRay that I was given for Christmas and my TV has a build in media server. Now that companies are actually getting interested in gaming on Linux I have no need for a console at all. I still think it's important to inform people about consumer rights being eroded away by companies like Microsoft and Sony. The other os was a major factor in my decision to buy the PS3 instead of an XBox or a Wii at the time. Having that removed several years after the purchase was a big slap in the face. The fall out of that is companies now including no class actions in their shrink wrap agreements. Huge loss for the consumer.

We wanted to say we'll still support a second controller for another hand to join in the game

That is in fact consoles' biggest advantage over PCs. Because consoles are more often connected to a monitor large enough to support two to four players offline, major labels are more likely to develop games that support two to four players offline for consoles than for PCs. Case in point: Where are the PC fighting games other than Street Fighter IV?

Sony and publishers of games on Sony's platforms have already been doing that since the PlayStation 2 by shutting off the matchmaking server of any game that's a couple years old. The most common error message is "DNAS error -103: This software title is not in service."